PASTEUR, KOCH, AND OTHERS 279 
tancous generation. To approach this question from the 
experimental side was to do a great service to science. 
The experiments of Redi were simple and homely. He 
exposed meat in jars, some of which were left uncovered, some 
covered with parchment, and others with fine wire gauze. The 
meat in all these vessels became spoiled, and flies, being at- 
tracted by the smell of decaying meat, laid eggs in that which 
was exposed, and there came from it a large crop of maggots. 
The meat which was covered by parchment also decayed in 
a similar manner, without the appearance of maggots within 
it; and in those vessels covered by wire netting the flies laid 
their eggs upon the wire netting. There they hatched, and 
the maggots, instead of appearing in the meat, appeared on 
the surface of the wire gauze. From this Redi concluded 
that maggots arise in decaying meat from the hatching of 
the eggs of insects, but inasmuch as these animals had been 
supposed to arise spontaneously within the decaying meat, the 
experiment took the ground from under that hypothesis. 
He made other observations on the generation of insects, 
but with acute scientific analysis never allowed his conclusions 
to run ahead of his observations. He suggested, however, 
the probability that all cases of the supposed production of life 
from dead matter were due to the introduction of living germs 
from without. The good work begun by Redi was confirmed 
and extended by Swammerdam (1637-1681) and Vallisnicri 
(1661-1730), until the notion of the spontaneous origin of any 
forms of life visible to the unaided eye was banished from 
the minds of scientific men. 
Redi (Fig. 89) was an Italian physician living in Arentino, 
distinguished alike for his attainments in literature and for 
his achievements in natural science. He was medical adviser 
to two of the grand dukes of Tuscany, and a member of the 
Academy of Crusca. Poetry as well as other literary com- 
positions shared his time with scientific occupations. His 
